1. Field of the Invention
The invention relates to sail reducing devices which operate by winding the sail on a tube, such as jib sail or main sail rollers for example.
2. Description of the prior art
In these devices, the sail hoist is fixed to the tube of the roller by a bolt rope and positioning of the sail, in other words hoisting thereof is effected by fitting the bolt rope into a longitudinal groove provided in the tube as the sail is gradually hauled towards the upper end of the tube by means of a halyard connected to the head of the sail. For hoisting the sail, the most sophisticated rollers use the jib sail halyard which forms part of the current basic rigging. So as to allow freedom of rotation between the head of the sail which rotates with the tube during operation of the roller and the halyard adjoining the mast, a swivel is inserted between these two latter; it comprises an inner part sliding on the tube and on which the head of the sail is fixed and an outer part guided for rotation about the preceding one and on which the halyard is bent.
The correct operation of the roller is only possible if the part of the swivel fixed to the halyard is subjected by this latter to a permanent resisting torque sufficient to avoid it being rotated during operation of the roller, since, because of the inevitable friction which appears at the level of the means which provides rotational guidance between the two parts of the swivel, the driving force causes the halyard to wrap itself round the tube and leads to jamming of the roller. In the known devices, the resistant torque can only be obtained if the halyard is stretched and moves substantially away from the axis of rotation of the roller. The first condition is not always respected by the user and the second can only be achieved on some boats whose halyard sheave is placed close to the point where the upper end of the shaft is fixed on which the tube of the roller rotates, by placing an additional guide pulley on the mast, so as to move the halyard away, which leads to a costly installation.
Furthermore, known rollers have two other disadvantages:
the first is the possibility of wear or jamming of associated halyards such as the spinnaker halyard on the swivel stop placed at the upper part of the tube; PA1 the second is that, during hoisting of the sail, in the case where the hoist of the sail is too long following a cutting error or extension thereof, they lead to jamming of the swivel on the stop which, under the considerable force due to hoisting of the sail, destroys the stop or disassembles the tube of the roller at its junctions.